What is the difference between the CPL and SPC ranks?

The difference is your command saw the potential for leadership so you are being promoted ( and it is a promotion) into a leadership spot as a Jr Non commissioned officer. No more shamming for you lol.

Thank all y’all for the information. I got my 5 yesterday so now I don’t have the CPL rank

When I was offered a promotion to E5 I had a lateral promotion to CPL until I finished BLC. As soon as i had my 1059 the PAR was published to promote me to SGT. Check to see if your in an E5 slot.

..and a BIG difference in the Guard and the Regulars...

Being CPL is basically having a job of a NCO but get paid as SPC. We have one in our unit who was CPL , now SGT he’s smarter than other SGTs take advantage of it and work to prove that you can be an effective E5

Just fer chuckles...

GHard stripe actually has more command and control than a Sp 4. As a junior NCO [promotable] there'll be more respect there than any "Full bird private" ever got. In an NBC room , for example, certain documentation cannot be signed for by a SP 4 , but a corporal can get it done.

you're in a NCO position

The Corporal is an NCO a Specialist 4 isn't.

I was also in the Guard when they pinned me with CPL. The unit needed more NCO's and I was the most Senior Specialist. In reality, I was ADHOC promoted to SFC with a Medical PLatoon of 32 in a Conventional Infantry BN before the BN transformed to the Light Infantry Configuration. It was nerve-racking at first. Expected to attend all the Sr. NCO functions..like NCO DP, the Tuesday Night Training Meetings before Drill (Non-Paid). I was a bit older than the average CPL 27 years old, So really it was making sure the medical support was in place for the Infantry Companies when they had training, Our Companies were spread out all over the State...so it was about loading up the Ambulances and getting them to their training locations and determining what other support was available. (ie) MEDEVAC, Air and Ground...Local Medical Facilities...and just normal Pre-Combat Checks. After a while it got to me, b/c the NCOs that were on our manning document never showed up or were TDY (ANCOC, BNCOC, PLDC) or whatever. I was then Promoted to SGT, but I had to play CPL for about three years before that happened. Promotions were slow as molasses in a New York Winter. It's much better now that most states have centralized promotions.